PITTSBURGH (AP) — The Pittsburgh Zoo & PPG Aquarium says the mother of a 2-year-old boy fatally mauled in a wild African dogs exhibit is to blame for her son’s death and shouldn’t be allowed to sue.

The claim filed Monday in the Allegheny County Court of Common Pleas comes in response to a wrongful-death lawsuit brought by the parents of Maddox Derkosh, who died Nov. 4 after falling over a 4-foot-tall railing into the exhibit when his mother lifted him up to get a better look.

“The injuries and damages sustained by Maddox Derkosh, including Maddox Derkosh’s death, were caused solely by the carelessness, negligence, and/or recklessness of Elizabeth Derkosh,” the zoo’s attorney wrote in the court filing. She “knew or should have known he could fall into the exhibit” and failed “to maintain a proper grasp of Maddox Derkosh after lifting him over the railing.”

The parents’ attorney, Robert Mongeluzzi, said in a statement Wednesday that “the zoo’s position is dead wrong and shameful.”

Prosecutors investigating the death of the boy called his death a “tragic accident” and said they wouldn’t prosecutor his mother.

Allegheny County District Attorney Stephen A. Zappala Jr. said Maddox had vision problems and wore glasses, and that’s partly why his mother had lifted him on a railing to view the pack of African painted dogs. Zappala said witnesses described the boy lunging forward, as if he thought there was some sort of clear barrier to stop him. The boy fell and the animals immediately pounced on the child, who bled to death.

Jason and Elizabeth Derkosh are seeking unspecified damages in their lawsuit, which also alleges negligence.